// @file key.h class(es) representing individual keys in a btree

/**
*    Copyright (C) 2011 10gen Inc.
*
*    This program is free software: you can redistribute it and/or  modify
*    it under the terms of the GNU Affero General Public License, version 3,
*    as published by the Free Software Foundation.
*
*    This program is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*    GNU Affero General Public License for more details.
*
*    You should have received a copy of the GNU Affero General Public License
*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*
*    As a special exception, the copyright holders give permission to link the
*    code of portions of this program with the OpenSSL library under certain
*    conditions as described in each individual source file and distribute
*    linked combinations including the program with the OpenSSL library. You
*    must comply with the GNU Affero General Public License in all respects for
*    all of the code used other than as permitted herein. If you modify file(s)
*    with this exception, you may extend this exception to your version of the
*    file(s), but you are not obligated to do so. If you do not wish to do so,
*    delete this exception statement from your version. If you delete this
*    exception statement from all source files in the program, then also delete
*    it in the license file.
*/

#pragma once

#include "mongo/db/jsobj.h"
#include "mongo/util/debug_util.h"

namespace mongo {

/** Key class for precomputing a small format index key that is denser than a traditional BSONObj.

    KeyBson is a legacy wrapper implementation for old BSONObj style keys for v:0 indexes.

    KeyV1 is the new implementation.
*/
class KeyBson /* "KeyV0" */ {
public:
    KeyBson() {}
    explicit KeyBson(const char* keyData) : _o(keyData) {}
    explicit KeyBson(const BSONObj& obj) : _o(obj) {}
    int woCompare(const KeyBson& r, const Ordering& o) const;
    BSONObj toBson() const {
        return _o;
    }
    std::string toString() const {
        return _o.toString();
    }
    int dataSize() const {
        return _o.objsize();
    }
    const char* data() const {
        return _o.objdata();
    }
    BSONElement _firstElement() const {
        return _o.firstElement();
    }
    bool isCompactFormat() const {
        return false;
    }
    bool woEqual(const KeyBson& r) const;
    void assign(const KeyBson& rhs) {
        *this = rhs;
    }
    bool isValid() const {
        return true;
    }

private:
    BSONObj _o;
};

class KeyV1Owned;

// corresponding to BtreeData_V1
class KeyV1 {
    // disallowed just to make people be careful as we don't own the buffer
    void operator=(const KeyV1&);
    // disallowed as this is not a great idea as KeyV1Owned likely will go out of scope
    KeyV1(const KeyV1Owned&);

public:
    KeyV1() {
        _keyData = 0;
    }
    ~KeyV1() {
        DEV _keyData = (const unsigned char*)1;
    }

    KeyV1(const KeyV1& rhs) : _keyData(rhs._keyData) {
        dassert(_keyData > (const unsigned char*)1);
    }

    // explicit version of operator= to be safe
    void assign(const KeyV1& rhs) {
        _keyData = rhs._keyData;
    }

    /** @param keyData can be a buffer containing data in either BSON format, OR in KeyV1 format.
               when BSON, we are just a wrapper
    */
    explicit KeyV1(const char* keyData) : _keyData((unsigned char*)keyData) {}

    int woCompare(const KeyV1& r, const Ordering& o) const;
    bool woEqual(const KeyV1& r) const;
    BSONObj toBson() const;
    std::string toString() const {
        return toBson().toString();
    }

    /** get the key data we want to store in the btree bucket */
    const char* data() const {
        return (const char*)_keyData;
    }

    /** @return size of data() */
    int dataSize() const;

    /** only used by geo, which always has bson keys */
    BSONElement _firstElement() const {
        return bson().firstElement();
    }
    bool isCompactFormat() const {
        return *_keyData != IsBSON;
    }

    bool isValid() const {
        return _keyData > (const unsigned char*)1;
    }

protected:
    enum { IsBSON = 0xff };
    const unsigned char* _keyData;
    BSONObj bson() const {
        dassert(!isCompactFormat());
        return BSONObj((const char*)_keyData + 1);
    }

private:
    int compareHybrid(const KeyV1& right, const Ordering& order) const;
};

class KeyV1Owned : public KeyV1 {
    void operator=(const KeyV1Owned&);

public:
    /** @obj a BSON object to be translated to KeyV1 format.  If the object isn't
             representable in KeyV1 format (which happens, intentionally, at times)
             it will stay as bson herein.
    */
    KeyV1Owned(const BSONObj& obj);

    /** makes a copy (memcpy's the whole thing) */
    KeyV1Owned(const KeyV1& rhs);

private:
    StackBufBuilder b;
    void traditional(const BSONObj& obj);  // store as traditional bson not as compact format
};
};
